Fibreglass kayak building

Discussion in 'Fiberglass and Composite Boat Building' started by lisa_w, Aug 19, 2006.

  1. lisa_w
    Joined: Aug 2006
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    lisa_w New Member

    Hey, i'm pretty new at this, i was wondering if i can get some info about building fibreglass kayaks. I want to build a moderate sized sea kayak. I have built surfboards before, had no trouble. I just really have no idea on how i make the molds for the kayaks. i have a friend building a wooden kayak, i dont really want something wooden. So basically if anyone could help me out that would be awesome, any tips help.
     
  2. frosh
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    frosh Senior Member

    Hi Lisa, No-one in their right mind builds a fibreglass kayak (one only) by first building a mold and then taking a single kayak off the mold. What is wrong with a wooden boat anyway. I will give you a web site that sells plans and kits for wooden kayaks of many different designs of very high quality.
    You can always sheath the outer surface in fibreglass if you want a tougher surface finish.
    Any way, even if you could borrow a mold, the chances that your first attempt to produce a boat off the mold, unless you had expert help would not give you a really good result.
    I would go with a kit, as the quality of the finished product is virtually guaranteed as is the design, because you have some construction experience already.
    http://www.clcboats.com/boats/shearwater.php :)
     
  3. marshmat
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    marshmat Senior Member

    Welcome aboard, Lisa- good to see another Canadian around!
    Building moulds is essentially like building three whole boats. The first step is to make a plug- essentially an exact replica of the part you want, made from whatever materials you're able to work. I'm doing some out of monolithic blocks of MDF board right now, it's very tedious. Then you make a fibreglass mould from that plug, and give it enough of a backing structure that it can't flex at all. Then you make the boat in that mould. As you can see it's quite an efficient way of making a lot of identical boats, but it doesn't work too well for making a single boat. There are ways of getting the mould directly provided the shape isn't too complicated, but they're all kind of tricky and require a lot of careful hand fairing as well as being pricey.
    If you don't want wood (and there are some really, really strong, light and gorgeous wooden canoes and kayaks out there), or glass-over-wood, a kit is probably a much cheaper and less stressful way to go for a single composite hull.
     
  4. lisa_w
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    lisa_w New Member

    Thanks.

    actually i wasnt just going to make one boat, i was a little worried about copying someone else's design, i was thinking of making about 6-12. I dont actually know what the laws are on taking a mould from someone else's kayak design, but i think it would be a crappy thing to do.
     
  5. Sean B.
    Joined: Jul 2006
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    Sean B. Junior Member

    what I would do if building a one-off sit-in style kayak in glass....

    glue blocks of (either expanded or extruded) styrene foam together to get the overall size.... shape the foam to the shape of the kayak you want (same process as shaping a board... planer, surform, sandpaper)... completely encase it in epoxy/glass composite... now you have sort of a pontoon.

    after the resin has completely cured, cut out your cockpit and whatever hatches you want and remove the fiberglass piece from the cockpit & hatch holes.... using either mineral spirits or acetone (you could use gasoline too, but I wouldn't at today's prices), pour it into the holes you just made. now you can scoop (or pour) out the styrene.... the acetone reacts with the styrene and basically "melts" it away into a gel/liquid form.

    I believe this process is called "lost mold"... works great for a one-off, but kind of messy.
     
  6. marshmat
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    marshmat Senior Member

    This is called 'splashing', and it is both illegal and disrespectful to do so. If you're thinking about perhaps building a fleet with some friends, then you could probably negotiate a very reasonable royalty with the designer of a boat you like. Or you could design your own although then you need to learn a lot about how to do so.... If you're thinking of building boats for profit, then I'd quietly lay such dreams aside for the moment as "profitable boatbuilding" is an oxymoron of the same type as "honest politician" or "military intelligence".
     
  7. frosh
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    frosh Senior Member

    Hi Lisa, I don't like the sound of the lost mold method for at least 3 reasons.
    Firstly it wont give you ability to build several boats economically. Second it is difficult to get a fair shape by carving polystyrene and very messy to plane or sand. Thirdly acetone attacks epoxy resin strongly even after it is set and softens the surface leaving it sticky.
    Another idea is to go to a canoe building factory and make an arrangement to rent a good quality mold providing they have the ownership over the design. :)
     
  8. JEM
    Joined: Jan 2004
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    JEM Senior Member

    I did a decked canoe design for a customer who wants to do exactly what you're doing.

    He's using the method prescribed in the book Building Your Kevlar Canoe: A Foolproof Method and Three Foolproof Designs

    Toughest part will be assembling the deck to the main hull. But since it's using a male mold and building only one, you can take the time to do it and make it look nice without having to worry about production time constraints.
     
  9. jasman
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    jasman Junior Member

    I'm yet another Canadian. I just recently purchased some molds and hope to learn how to fibreglass them. I've posted a couple of questions looking for help in learning how to fibreglass.
    Are you near Peterborough by chance?
     
  10. JEM
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    JEM Senior Member

    me? No. North Carolina, USA.
     
  11. unifab1
    Joined: Apr 2012
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    unifab1 New Member

    building with foam

    You need a hot wire and pour foam, pour block and shape.
     
  12. icoulddothat
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    icoulddothat Junior Member

    Would this work for a small boat?


    Would this work for a small boat? Using sheets of rigid insulation board as the base foam and carving the boat out of it then glassing it?
     
  13. Petros
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    Petros Senior Member

    you could carve any boat hull shape out of large block of foam, and than glass it. But there are more efficient ways to do it. Using foam strips in a similar way that wood strip built hulls are made is one way, the other is to use foam strips in a way that cold molded wood and fibreglass boats are made.

    Build a set of plywood or particleboard molds, lay over it strips of foam diagonally, one layer in each direction. Sand it smooth and than glass the outside. Remove the frame work and than glass the inside with bulkheads, air tight chambers, etc. No reason why strips of foam can not be used the same way cedar strips are used. However, you want the foam to be thicker than you would use cedar to compensate for the lower strength of the foam.
     
  14. Tony Eaton
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    Tony Eaton Junior Member

    http://www.paddlinglight.com/kayak-and-canoe-plans/

    From this page I see some historical hull designs for free or donation or for a nominal fee. (You could ask them, it seems like they would be flattered to get some pictures of your results?) It seems like plywood stitch and glue would be the easiest way to build a mold but there are a lot of ways once you have the measurements. You could skip the epoxy and fiberglass and just use titebond and fabric reinforced with duct tape as needed.
     

  15. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    Have you guys noticed Lisa hasn't been interested since 2006 ?
     
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